Name: optimized procedure for determining the adsorption of phosphonates onto granular ferric hydroxide using a miniaturized phosphorus determination method
Uploaded: 2018-05-18T14:00:00.000+00:00
Duration: 8 min 21 s
Description: Watch this Scientific Journal Video about Optimized Procedure for Determining the Adsorption of Phosphonates onto Granular Ferric Hydroxide using a Miniaturized Phosphorus Determination Method at JoVE

The authors are grateful for the financial support by the Willy-Hager-Stiftung, Stuttgart. We would also like to thank the employees of Zschimmer &amp; Schwarz Mohsdorf GmbH &amp; Co. KG for providing phosphonate samples.

1. Preparation of All Required Solutions for the Total P Determination
NOTE: The preparation of some of the solutions described below is explained in ISO 687828. These preparation methods have been slightly adapted to the method of this work. The required degree of purity of chemicals can be found in the attached material list.
<ol>
	<li>Preparation of H2SO4 solutions (13.5, 9 and 0.9 M H2SO4) 
	Caution: Work under fume hood.
	<ol>
		<li>Preparation of 13.5 M H2SO4
		<ol>
			<li>Fill a 100 mL graduated cylinder with 25 mL of water and transfer it into a 100 mL glass bottle surrounded by ice cubes placed in a beaker.</li>
			<li>Fill the same graduated cylinder with 75 mL of concentrated sulfuric acid and transfer it under stirring to the water in the bottle. Caution: Heat development.</li>
			<li>Take the bottle carefully out of the beaker as soon as it is sufficiently cooled down (max. 40 &#176;C).</li>
		</ol>
		</li>
		<li>Preparation of 9 M H2SO4 (required for the preparation of molybdate solution)
		<ol>
			<li>Fill a 1 L graduated cylinder with 700 mL of water and transfer it into a 3 L glass beaker surrounded by ice cubes placed in a bucket.</li>
			<li>Fill the same 1 L graduated cylinder with 700 mL of concentrated sulfuric acid and transfer it under stirring to the water in the 3 L beaker. Caution: Heat development.</li>
			<li>Take the 3 L beaker carefully out of the bucket as soon as it is sufficiently cooled down (max. 40 &#176;C) and transfer its content into a 2 L glass bottle.</li>
		</ol>
		</li>
		<li>Preparation of 0.9 M H2SO4
		<ol>
			<li>Fill a 250 mL volumetric flask with about 100 mL of water.</li>
			<li>Transfer 25 mL of 9 M H2SO4 (see 1.1.2) into the 250 mL volumetric flask using a 25 mL volumetric pipette. Caution: Heat development.</li>
			<li>Fill the 250 mL volumetric flask with water up to the 250 mL ring mark.</li>
			<li>Close the volumetric flask with a stopper, shake it several times for homogenization and transfer the content of the volumetric flask into a 250 mL glass bottle.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Preparation of HCl rinsing solution (approx. 2 M) 
	Caution: Work under fume hood.
	<ol>
		<li>Fill a 2 L graduated cylinder with 1 L of water.</li>
		<li>Fill this graduated cylinder with 400 mL of 32% HCl (w/w) solution.</li>
		<li>Now add 600 mL of water to gain a total volume of 2 L in the graduated cylinder.</li>
		<li>Stir the content of the graduated cylinder with a rod (e.g., graduated pipette) and transfer the content of the graduated cylinder into a 2.5 L glass bottle.</li>
		<li>Close the bottle and shake it upside down several times for homogenization.</li>
		<li>Reuse this solution only until a color change becomes apparent. Then discard the rinsing solution and prepare a new one.</li>
	</ol>
	</li>
	<li>Preparation of HCl solutions (10.2 and 2 M) 
	Caution: Work under fume hood.
	<ol>
		<li>Use 32% HCl (w/w) as 10.2 M HCl.</li>
		<li>Preparation of 2 M HCl
		<ol>
			<li>Fill a 100 mL volumetric flask with 15 mL of 32% HCl (10.2 M) using a 15 mL volumetric pipette.</li>
			<li>Add another 4.67 mL of 32% HCl (10.2 M) to the volumetric flask using a micropipette.</li>
			<li>Fill the volumetric flask with water up to the 100 mL ring mark.</li>
			<li>Close the volumetric flask with a stopper and shake it upside down several times for homogenization and transfer the content of the volumetric flask into a 100 mL glass bottle.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Preparation of NaOH solutions (10, 2, 1.5 M NaOH) 
	Caution: Work under fume hood.
	<ol>
		<li>Weigh 100.0 g (for 10 M), 20 g (for 2 M) or 15 g (for 1.5 M) of NaOH into a small beaker and transfer the content of the beaker into a 250 mL volumetric flask.</li>
		<li>Fill the volumetric flask with water up to the 250 mL ring mark. Close the volumetric flask with a stopper and shake it upside down several times for homogenization (Caution: solution can become hot). If the height of the water level no longer corresponds to the ring mark, add more water (the total volume changes as a result of the dissolving process).</li>
		<li>Transfer the content of the volumetric flask into a 250 mL plastic bottle (Caution: Do not use glass bottles for NaOH solutions).</li>
	</ol>
	</li>
	<li>Preparation of K2S2O8 solution/suspension (8.33, 41.67, 50.00, 58.33, 66.66 g/L) 
	NOTE: Differently concentrated peroxodisulfate mixtures are required for phosphorus determination. Since some of them are above the saturation limit of K2S2O8 of approx. 50 g/L at 20 &#176;C, it is advisable to weigh the K2S2O8 directly into a brown glass bottle and pour a corresponding volume of water over it (do not use volumetric flasks for the preparation).
	<ol>
		<li>Weigh 2.08 g (for 8.33 g/L), 10.42 g (41.67 g/L), 12.50 (50.00 g/L), 14.58 g (58.33 g/L) or 16.67 g (66.66 g/L) of solid K2S2O8 directly into a brown 250 mL glass bottle.</li>
		<li>Fill a graduated cylinder with 250 mL of water and pour this water over the K2S2O8 in the bottle.</li>
		<li>Stir the content of the bottle until all ingredients are dissolved or until there is only a slight turbidity.</li>
		<li>Carry out the extraction of K2S2O8 under high turbulence on the magnetic stirrer to ensure that the undissolved K2S2O8 can also be extracted as homogeneously as possible.</li>
	</ol>
	</li>
	<li>Preparation of 100 g/L ascorbic acid solution
	<ol>
		<li>Weigh 50 g of ascorbic acid into a 500 mL volumetric flask.</li>
		<li>Fill the volumetric flask with water up to the 500 mL ring mark.</li>
		<li>Stir the content of the volumetric flask on the magnetic stirrer until the ascorbic acid is completely dissolved. It may be necessary to correct the level of the water surface to make it congruent with the ring mark by adding a little more water (be careful of the stirring bar giving volume as well). Then transfer the content of the volumetric flask into a brown 500 mL glass bottle.</li>
	</ol>
	</li>
	<li>Preparation of Molybdate I solution (required for phosphate determination)
	<ol>
		<li>Weigh 13.0 g of solid (NH4)6Mo7O24&#8729;4H2O directly into a 100 mL glass bottle. Fill a graduated cylinder with 100 mL of water and pour it into the bottle. Stir the content of the bottle on a magnetic stirrer until it is completely dissolved.</li>
		<li>Weigh 0.35 g of solid K(SbO)C4H4O6&#8729;&#189;H2O directly into a fresh 100 mL glass bottle. Fill a graduated cylinder with 100 mL of water and pour it into the bottle with K(SbO)C4H4O6&#8729;&#189;H2O. Stir the content of the bottle until it is completely dissolved.</li>
		<li>Fill a graduated cylinder with 300 mL of 9 M H2SO4 (see 1.1.2) and pour it into a brown 500 mL glass bottle.</li>
		<li>Add the (NH4)6Mo7O24&#8729;4H2O solution to the 300 mL of 9 M H2SO4. Then add the K(SbO)C4H4O6&#8729;&#189;H2O solution to this mixture. Close the bottle and shake it several times upside down for homogenization.</li>
	</ol>
	</li>
	<li>Preparation of Molybdate II solution (required for total P determination)
	<ol>
		<li>Weigh 13.0 g of solid (NH4)6Mo7O24&#8729;4H2O directly into a 100 mL glass bottle. Fill a graduated cylinder with 100 mL of water and pour it into the bottle. Stir the content of the bottle on a magnetic stirrer until it is completely dissolved.</li>
		<li>Weigh 0.35 g of solid K(SbO)C4H4O6&#8729;&#189;H2O directly into a fresh 100 mL glass bottle. Fill a graduated cylinder with 100 mL of water and pour it into the bottle with K(SbO)C4H4O6&#8729;&#189;H2O. Stir the content of the bottle until it is completely dissolved.</li>
		<li>Fill a graduated cylinder with 70 mL of water. Add 230 mL of 9 M H2SO4 (see 1.1.2) to the water in the graduated cylinder (i.e., fill up to 300 mL). Carefully homogenize the content of the graduated cylinder with a rod (e.g., graduated pipette). Transfer the content of the graduated cylinder into a brown 500 mL glass bottle (current content: 6.9 M H2SO4).</li>
		<li>Add the (NH4)6Mo7O24&#8729;4H2O solution to the 300 mL of 6.9 M H2SO4. Then add the K(SbO)C4H4O6&#8729;&#189;H2O solution to this mixture. Close the bottle and shake it several times upside down for homogenization.</li>
	</ol>
	</li>
	<li>Preparation of internal quality standard (IQS: 1 mg/L KH2PO4-P in 0.9 mM H2SO4)
	<ol>
		<li>Dry a few grams of KH2PO4 in a small glass dish at 105 &#176;C in the drying oven until mass constancy is achieved and then cool the KH2PO4 down to room temperature in a desiccator.</li>
		<li>Weigh 0.2197 g &#177; 0.0002 g of KH2PO4 directly from the desiccator into a 1 L volumetric flask and add approx. 800 mL of water into the volumetric flask.</li>
		<li>Now add 5 mL of 9 M H2SO4 (see 1.1.2) to the flask using a 5 mL volumetric pipette and fill the flask with water up to the 1 L ring mark.</li>
		<li>Stir the content of the volumetric flask on the magnetic stirrer and transfer the content of the volumetric flask into a 1 L glass bottle (current content: 50 mg/L KH2PO4-P in 45 mM H2SO4). This solution can henceforth be used as a stock solution for the preparation of IQS.</li>
		<li>Transfer 10 mL of this solution into a 500 mL volumetric flask using a 10 mL volumetric pipette, fill the volumetric flask with water up to the 500 mL ring mark and stir the content of the volumetric flask on the magnetic stirrer.</li>
		<li>Transfer the content of the volumetric flask into a 500 mL glass bottle (current content: 1 mg/L KH2PO4-P in 0.9 mM H2SO4). This solution is the IQS.</li>
	</ol>
	</li>
</ol>
2. Preparation of Phosphonate-Containing Buffered Solutions
<ol>
	<li>Weigh or pipette the desired buffer into a volumetric flask (at a target concentration of 0.01 M buffer in 1 L, e.g.: 572 &#181;L of 100% AcOH, 2.1014 g of CitOH&#183;H2O, 1.9520 g of MES, 2.0926 g of MOPS, 2.3831 g of HEPES, 2.5233 g of EPPS, 2.3732 g of CAPSO, 2.2132 g of CAPS, 5 mL of 2 M NaOH).</li>
	<li>Fill the volumetric flask to about three quarters with water and add a previously prepared 1 g/L phosphonate-P stock solution (for a target concentration of 1 mg/L P in 1 L, e.g., 1 mL of 1 g/L phosphonate-P).</li>
	<li>Fill the flask with water up to the ring mark, stir the content of the flask on the magnetic stirrer until all ingredients are dissolved and transfer it into a glass bottle.</li>
	<li>While stirring, adjust the desired pH value in the buffer solution (e.g., pH 6 at MES) with HCl (e.g., 2 and 10.2 M) or NaOH (e.g., 2 and 10 M) (the addition of both acidic and basic solution should be avoided to prevent an unnecessary increase of ionic strength).</li>
	<li>To determine the phosphonate-P concentration, proceed according to step 4.</li>
</ol>
3. Procedure of the Adsorption Test
<ol>
	<li>Wash the filter material thoroughly with distilled water (e.g., over a sieve with a mesh size of 0.5 mm) and then dry it at 80 &#176;C. 
	Note: The protocol can be paused here.</li>
	<li>Weigh the filter material (e.g., granular ferric hydroxide) into a 50 mL centrifuge tube. 
	Note: The protocol can be paused here.</li>
	<li>Quickly fill the 50 mL centrifuge tube with the phosphonate-containing solution from step 2 up to the 50 mL mark.</li>
	<li>Quickly close the tube and clamp it into the running rotator (the contact time starts from now on).</li>
	<li>Rotate the tube at 20 revolutions per minute for a specific amount of time (e.g., 1 h).</li>
	<li>Filter approx. 10-20 mL of the supernatant with a syringe filter (0.45 &#181;m pore size) into an empty glass bottle. 
	Note: The protocol can be paused here.</li>
	<li>Determine the pH value of the filtrate and to determine the phosphonate-P concentration proceed with step 4. In the case of investigating phosphate adsorption, proceed with step 5.</li>
</ol>
4. Determination of Total P (Phosphonate-P) According to ISOmini
NOTE: The following procedure is also shown in Figure 3.
<ol>
	<li>Transfer an aliquot of the sample to be analyzed (Vsample, max. 4 mL) using a micropipette into a 10 mL screw cap vial (the vial including the cap should be pre-rinsed with HCl (see 1.2) and H2O and dried at 80-100 &#176;C). 
	Note: The protocol can be paused here.</li>
	<li>Add water with a micropipette to obtain a total volume of 4 mL together with the sample previously added (Vwater = 4 mL-Vsample). 
	Note: The protocol can be paused here.</li>
	<li>Add 0.2 mL of 0.9 M H2SO4 solution (see 1.1.3) using a micropipette. If there is a concentration of 1 M NaOH in the sample, as is often the case with regeneration solutions, add 0.2 mL of 13.5 M H2SO4 solution (see 1.1.1) (Caution: This solution of sulfuric acid is highly concentrated). 
	Note: The protocol can be paused here.</li>
	<li>Add 4.8 mL of a K2S2O8 solution/suspension (see 1.5) the concentration of which depends on the buffer contained in the sample (corresponding to ISO at 0.01-1 M NaOH: 8.33 g/L K2S2O8; 0.01 M CitOH, AcOH, MES: 41.67 g/L; 0.01 M MOPS: 50.00 g/L; 0.01 M HEPES: 58.33 g/L; 0.01 M EPPS, CAPSO, CAPS: 66.66 g/L).</li>
	<li>Close the vial with the cap very tightly and shake it.</li>
	<li>Heat the vial in a thermostat at 148-150 &#176;C for 1 h.</li>
	<li>Take the vial out of the thermostat and let it cool down to room temperature. 
	Note: The protocol can be paused here.</li>
	<li>Open the vial and add 0.4 mL of 1.5 M NaOH solution (see 1.4). 
	Note: The protocol can be paused here.</li>
	<li>Add 0.2 mL of 100 g/L ascorbic acid solution (see 1.6).</li>
	<li>Subsequently, add 0.4 mL molybdate II solution (see 1.8).</li>
	<li>Close the vial and turn it upside down for homogenization.</li>
	<li>Wait minimum 15 minutes to a maximum of 4 h for color formation.</li>
	<li>Measure spectral absorbance (A) at a wavelength of 880 nm using a photometer.</li>
	<li>Carry out the steps 4.1-4.13 regularly for 4 mL of water (for the determination of Ablind) as well as for 4 mL of an IQS (see 1.9).</li>
	<li>Calculate the total P or phosphonate-P concentration of the analysis sample on the basis of the specific absorbance of the analysis sample (A), the absorbance of the blind sample (Ablind) and the sample volume (Vsample) using the following equation (0.287 corresponds to the slope of the calibration line with 1 cm cuvettes and can deviate depending on the photometer): 
	<img alt="Equation 2" src="/files/ftp_upload/57618/57618eq2v2.jpg" /></li>
</ol>
5. Determination of o-PO43--P According to ISOmini
NOTE: This determination method can be used when the adsorption of inorganic ortho-phosphate on granulated filter materials is to be investigated. In this case, the sample to be tested does not have to be digested.
<ol>
	<li>Transfer an aliquot of the sample to be analyzed (Vsample, max. 9.4 mL) by means of a micropipette into a 10 mL screw cap vial (the vial including the cap should be pre-rinsed with HCl (see 1.2) and H2O and dried at 80-100 &#176;C). 
	Note: The protocol can be paused here.</li>
	<li>Add water with a micropipette to obtain a total volume of 9.4 mL together with the sample previously added (Vwater = 9.4 mL-Vsample). 
	Note: The protocol can be paused here.</li>
	<li>Add 0.2 mL of 100 g/L ascorbic acid solution (see 1.6).</li>
	<li>Subsequently, add 0.4 mL of molybdate I solution (see 1.7).</li>
	<li>Close the vial and turn it upside down for homogenization.</li>
	<li>Wait minimum 15 minutes to a maximum of 4 h for color formation.</li>
	<li>Measure spectral absorbance (A) at a wavelength of 880 nm using a photometer.</li>
	<li>Carry out the steps 5.1-5.7 regularly for 9.4 mL of water (for the determination of Ablind) as well as for 4 mL of an IQS (see 1.9).</li>
	<li>On the basis of the specific absorbance of the analysis sample (A), of the blind sample (Ablind) and the sample volume (Vsample), the ortho-phosphate-P concentration of the analysis sample can be calculated using the equation in 4.15.</li>
</ol>

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P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+modified+single+solution+method+for+the+determination+of+phosphate+in+natural+waters.">A modified single solution method for the determination of phosphate in natural waters.</a> Analytica Chimica Acta. 27, 31-36 (1961).</li><li>Worsfold, P., McKelvie, I., Monbet, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+phosphorus+in+natural+waters:+A+historical+review.">Determination of phosphorus in natural waters: A historical review.</a> Analytica Chimica Acta. 918, 8-20 (2016).</li><li>Going, J. E., Eisenreich, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spectrophotometric+studies+of+reduced+molybdoantimonylphosphoric+acid.">Spectrophotometric studies of reduced molybdoantimonylphosphoric acid.</a> Analytica Chimica Acta. 70, 95-106 (1974).</li><li>Pai, S. C., Yang, C. C., Riley, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+acidity+and+molybdate+concentration+on+the+kinetics+of+the+formation+of+the+phosphoantimonylmolybdenum+blue+complex.">Effects of acidity and molybdate concentration on the kinetics of the formation of the phosphoantimonylmolybdenum blue complex.</a> Analytica Chimica Acta. 229, 115-120 (1990).</li><li>Eisenreich, S. J., Bannerman, R. T., Armstrong, D. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+simplified+phosphorus+analysis+technique.">A simplified phosphorus analysis technique.</a> Environmental Letters. 9 (1), 43-53 (1975).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> ISO 6878:2004. Water quality-Determination of phosphorus-Ammonium molybdate spectrometric method. , (2004).</li><li>Freundlich, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=&#220;ber+die+Adsorption+in+L&#246;sungen+(About+the+adsorption+in+solutions).">&#220;ber die Adsorption in L&#246;sungen (About the adsorption in solutions).</a> Z. Physical Chemistry. 57, 385-470 (1907).</li><li>Ho, Y. S., Porter, J. F., McKay, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Equilibrium+isotherm+studies+for+the+sorption+of+divalent+metal+ions+onto+peat:+Copper,+nickel+and+lead+single+component+systems.">Equilibrium isotherm studies for the sorption of divalent metal ions onto peat: Copper, nickel and lead single component systems.</a> Water Air &amp; Soil Pollution. 141 (1-4), 1-33 (2002).</li><li>Li, L., Zhang, S., Li, G., Zhao, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+chemical+oxygen+demand+of+nitrogenous+organic+compounds+in+wastewater+using+synergetic+photoelectrocatalytic+oxidation+effect+at+TiO2+nanostructured+electrode.">Determination of chemical oxygen demand of nitrogenous organic compounds in wastewater using synergetic photoelectrocatalytic oxidation effect at TiO2 nanostructured electrode.</a> Analytica Chimica Acta. 754, 47-53 (2012).</li></ol>

No conflicts of interest declared.

The increasing significance of phosphonates requires research for reliable methods of removing these compounds from wastewater to protect wastewater treatment plants or receiving water bodies. At present, very few studies have been carried out on the removal of phosphonates from industrial wastewater5,11,12,13,14,16. The procedure presented here shows that investigations regarding the elimination of phosphonates by adsorption on polar iron oxide containing materials, in particular granular ferric hydroxide, can be carried out quickly and reliably when in accordance with the given protocol.
The decisive point in conducting adsorption studies is the maintenance of the pH value. This cannot be done in rotating centrifuge tubes without using a buffer. In this article, it was shown that Good buffers allow an acceptable pH adjustment only at a concentration of 0.01 M and even at this concentration have no significant influence on the adsorption of phosphonates onto GFH. The application of Good buffers is also the reason why the procedure presented here cannot be used for studies on adsorption of phosphonates onto rather non-polar materials such as activated carbon. Good buffers would compete with phosphonates for free adsorption sites.
Since the direct analysis of phosphonates by means of HPLC22 or IC-ICP-MS21 is very complex and expensive, the presented method suggests that the phosphonate after contact with the adsorbent should be measured indirectly via the determination of the total P. A standardized method (ISO 687828) is generally used for the total P determination, in which a digestion is carried out by means of H2SO4 and K2S2O8 on a hotplate, the pH value is then set to 3-10 by means of NaOH and a blue color complex (the color intensity of which is linearly proportional to the phosphate concentration) is formed with the aid of ascorbic acid and molybdate solution. This standardized method is very labor and time consuming, which is why a faster variant of the ISO method (ISOmini) was developed. The ISOmini method reduces the total volume to one-fifth. The digestion takes place comfortably in a thermostat and the NaOH dosage after digestion is fixed. This method enables a large number of phosphorus determinations to be carried out within a very short time and does not compromise accuracy in comparison to the ISO method.
Each buffer has a different COD. In addition, the relatively high necessary buffer concentration of 0.01 M means that, in order to ensure sufficient digestion of the sample constituents, considerably higher amounts of oxidizing agent have to be dosed than it is stipulated in the ISO method. If the K2S2O8 dosage is too low or too high, incorrect measurement results do occur. In the ISOmini method, this K2S2O8 dosage is thus matched to each buffer individually. Another critical point is the dosage of NaOH. As a rule, regeneration solutions have NaOH concentrations of &#62; 0.1 M. In order to avoid that the [H+]:[Mo] ratio required for the formation of the color complex25,26 is not adhered to, a proper adjustment of the H2SO4 quantity prior to digestion is therefore necessary. The problem arises when the regeneration solution is reused several times, thereby changing its pH value and COD. Since a reliable and simple pH measurement is not possible in screw cap vials and an appropriate pH adjustment is not provided, the ISOmini method presented here, thus, reaches its limits for samples with very high pH values. For regeneration solutions it is therefore recommended to use the ISO method.

Motivation
The efforts to reduce nutrient inputs into surface waters, which are necessary, inter alia, in the context of the implementation of the European Water Framework Directive1, require a more detailed examination of phosphorus emissions. The substance group of phosphonates (Figure 1), which are used as bleach stabilizers in textile and paper industries, as antiscalants in drinking water treatment, as hardness stabilizers of cooling water and in detergents and cleaning agents, is particularly relevant in terms of quantity and environmental relevance2. Phosphonates are suspected of contributing to long-term eutrophication of water bodies2,3,4. For example, due to UV radiation of sunlight or in the presence of MnII and dissolved oxygen, phosphonates can be degraded into microbiologically available phosphates5,6. The oversupply of phosphate is an essential characteristic of ecologically unbalanced water bodies, which makes phosphorus an important target substance for the sustainable improvement of the ecological status of water bodies.
Phosphonates can be removed from wastewater by precipitation/flocculation when using iron or aluminum salts7,8,9,10. In this process, metals are transformed into hardly soluble metal hydroxides. These polar flocks with a relatively large specific surface serve as adsorbents for the negatively charged phosphonates. However, the flocculation process can have two main disadvantages. Depending on the wastewater, sludge volumes of up to 30% of the sample volume can occur11. This sludge has to be separated, treated and disposed of in a further sedimentation or filter stage. Furthermore, phosphonates can complex the added flocculants and thus prevent the formation of flocks, especially in wastewater with low water hardness. This effect can be compensated by increased quantities of flocculant. However, this leads to increased &#946; values (&#946; = molar ratio of flocculant to phosphorus in wastewater)11,12. A complex wastewater matrix, therefore, can complicate the control of an optimum flocculant dosage.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/57618/57618fig1.jpg" /> 
Figure 1: Structural formulae of important phosphonates11. <a href="/files/ftp_upload/57618/57618fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
A possible alternative that exploits the high adsorption affinity of phosphonates to metal-containing surfaces and that does not have the above-mentioned disadvantages are filter materials based on iron (hydr)oxides. For such filter materials, the literature mainly presents investigations into the elimination of phosphate13,14,15,16. This paper introduces a procedure which allows the investigation of the adsorption capacity of selective granulated filter materials, in this work in particular with granular ferric hydroxide (GFH), regarding phosphonates with little workload and significant cost saving. The study of the adsorption capacity can be divided into the following steps: preparation of the phosphonate solution, adsorption test (contact of the phosphonate solution with the granulate) and phosphonate analysis. All steps must be perfectly coordinated.
Concept for adsorption test and the use of suitable buffers 
For the study of adsorption capacity, batch or column tests can be carried out. In order to determine adsorption isotherms or pH-dependencies of the adsorbent, the batch approach is preferred since many results can be obtained within a short period of time by the possibility of varying several parameters. The pH value is one of the most important factors influencing adsorption. Compliance with or adjustment of the pH value is a great challenge for the laboratory technician, as the simple adjustment of the pH value in the sample solution previously to the contact with the adsorbent is usually not sufficient. Each adsorbent material is usually striving to approximate the pH around its point of zero charge (PZC). Accordingly, it is possible that an aqueous solution, e.g., adjusted to pH 3, changes to a pH value of 8 when in immediate contact with the adsorbent. Wastewater mostly has a natural buffering capacity, which attenuates this effect. If, however, only the removal of a particular target substance is to be investigated with a particular adsorbent, synthetic wastewater must be used, i.e., pure water, which is specifically spiked with the target substance or, e.g., competitive anions. In contrast to powdered adsorbents, where the pH value can be easily maintained in the desired range by adding acids and bases in the open stirring vessel, no pH adjustment in this form can be done in a batch approach with granulates. In order to keep granules homogeneously suspended, very high stirring speeds are required, which would result in very rapid abrasion of the material. If such abrasion is unintended, the gentlest method is to rotate closed centrifuge tubes to keep the granules mixed continuously in the solution. The only way to keep the pH value constant in this case is to use buffers.
The following requirements for buffers must be met in order to be able to investigate the adsorption of phosphate and phosphonates on iron-containing filter materials: free of phosphorus; colorless; soluble; at best, no complexing agents; no competition with phosphonates regarding adsorption onto polar filter materials; similar structure of the different buffers used; and buffers or their degradation products must not have a negative effect on the spectral absorbance of the color complex after digestion for total P determination. For the biochemical research field, so-called Good buffers were developed17,18,19, which have exactly these properties. Thus, for the investigations of this work, the buffers in Table 1 were selected. The pKa value of each buffer indicates the range that can be kept constant by the buffer. For the pH range &#60; 5, however, organic acids such as citric acid (CitOH) and acetic acid (AcOH) must be used. Citric acid is a complexing agent, but it buffers in a pH range where most iron-containing filter materials become unstable anyway. Acetic acid and MOPS were already used by Nowack and Stone7 to investigate the adsorption of NTMP on slurry goethite (&#945;-FeOOH) at pH 4.6 and 7.2. However, their experiments on the pH-dependency of adsorption took place without buffering.
<img alt="Table 1" src="/files/ftp_upload/57618/57618table1.jpg" /> 
Table 1: pKa values20, theoretical oxygen demand (ThOD) and analyzed actual chemical oxygen demand (COD) of buffers used in this study.
Total P determination (ISOmini) adapted to the buffer solution 
Following each adsorption test, each solution must be analyzed for the residual phosphonate concentration. Only recently, a method for the determination of phosphonates in environmental samples with limits of quantification in the range of 0.1 &#181;g/L was introduced. It is based on the IC-ICP-MS method and the use of cation exchangers (for the conversion of phosphonates into &#34;free&#34; phosphonic acids) and anion exchangers (for the pre-concentration of phosphonates)21. Furthermore, already in 1997 a method from Nowack22 was introduced with higher limits of detection of 15-100 &#181;g/L, which is based on the pre-complexation of phosphonates with FeIII, retention using HPLC and the photometric detection of these complexes. However, these methods are very time-consuming and expensive. In studies with synthetic wastewater in which the only phosphorus-containing compound is a phosphonate, it is sufficient to determine the phosphonate concentration by determining the total P concentration. The determination of inorganic phosphate presents the experimenter with far fewer problems than the determination of total P, as the latter requires previous digestion. The amount of chemicals that have to be added priorly must be matched precisely to the compounds present in the sample.
The determination of phosphate is currently carried out mainly using the method introduced by Murphy and Riley23. This method is based on the spectrophotometric detection of an intensely colored phosphomolybdenum blue complex ([PSb2Mo12O40]&#8722; with &#955;max at 880 nm) which is formed in the presence of phosphate and acidified molybdate using ascorbic acid and antimony(III) as reducing agents24. In other studies, the optimal ratio of [H+]:[Mo] was determined to be 60-8025,26. In order to determine total P, digestion, i.e., the breaking of P-O-P, C-O-P and C-P bonds in phosphorus-containing compounds and the oxidation of phosphorus to phosphate must be carried out prior to the phosphomolybdenum blue formation24. Eisenreich et al.27 presented a simplified method based on the use of the oxidizing agent peroxodisulfate (K2S2O8) in the acidic milieu. Many of these findings have been incorporated into the development of ISO 687828, which systematically explains the procedure for the determination of phosphate-P and total P concentrations in water samples (wastewater and seawater).
The total P determination according to ISO 6878 (Figure 2) requires the sample to be digested in an Erlenmeyer flask by K2S2O8 at an acidic pH (use of sulfuric acid) for at least 30 min. After digestion, the pH value is set to 3-10 using NaOH and the content of the Erlenmeyer flask is transferred to a 50 mL volumetric flask. In this flask, ascorbic acid and an acidic solution containing molybdate and antimony are added to the sample and then filled with water. After 10-30 minutes, the intensity of this blue coloration is measured at a wavelength of 880 nm. In the case of phosphate determination, the digestion is omitted. This means, the sample is mixed in a 50 mL volumetric flask with ascorbic acid and a solution containing molybdate as well as antimony, and the intensity of the blue coloration is measured in the photometer.
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/57618/57618fig2.jpg" /> 
Figure 2: Procedure of total P determination according to ISO 6878 applying digestion using sulfuric acid and potassium peroxodisulfate, a subsequent pH adjustment with NaOH and coloration using ascorbic acid and molybdate-containing solutions. <a href="/files/ftp_upload/57618/57618fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
The procedure of total P determination is very complex since during digestion it must always be taken care of that the sample does not boil over and the adjustment of the sample to pH 3-10 takes a long time. In order to be able to analyze as many samples as possible in a very short time, a miniaturized form of the total P and ortho-phosphate determination was developed based on this ISO method. Figure 3 summarizes the individual steps of this method. In this miniaturized determination method (ISOmini), the final volume of the color solution is 10 mL (in the ISO method, this is 50 mL). Accordingly, the ISOmini method reduces the amount of the solutions to be used to one-fifth. In the ISOmini method, the digestion is carried out in a thermostat (in contrast to the ISO method, where digestion is proposed in an Erlenmeyer flask on a hotplate) at 148-150 &#176;C to obtain the highest possible oxidation. NaOH is added after digestion together with the ascorbic acid and acidic molybdate solution.
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/57618/57618fig3.jpg" /> 
Figure 3: Procedure of total P determination according to a modified and miniaturized form of ISO 6878 (ISOmini) using 10 mL screw cap vials, buffer-dependent potassium peroxodisulfate concentrations, heating in a thermostat and addition of color reagents directly to the digested sample without transferring it previously. <a href="/files/ftp_upload/57618/57618fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
The organic buffers contained in the samples must be present in relatively high concentrations (10 mM) in comparison to the phosphonate (5-30 &#181;M) in order to maintain the pH value effectively. These buffers must be digested for the analysis of the total P after the adsorption test. Accordingly, the dosed amount of oxidizing agent must be matched to each buffer, taking into account that too much oxidizing agent should not interfere with the formation of the color complex formed after digestion. In order to be able to estimate the K2S2O8 quantity required for the digestion of each buffer in the total P determination based on the analyzed chemical oxygen demand (COD), a comparison of how many electrons can be converted during the reduction of O2 and K2S2O8 is necessary:
O2 + 4 H+&#160;+ 4 e-&#160;&#8594; 2 H2O
S2O82-&#160;+ 2 e-&#160;&#8594; 2 SO42-
Thus, the oxidation of a particular molecule requires twice as many peroxodisulfate molecules as O2 molecules. Accordingly, in the case of a sample volume of 20 mL, the COD of the sample must not exceed 500 mg/L when using the ISO method. However, even in the case of MES, the Good buffer with the smallest molar mass from Table 1, already a COD of 2.4 g/L is present at a concentration of 10 mM. In addition to the step-by-step protocol of the adsorption test and ISOmini method, this paper, therefore, investigates the required buffer concentration, the influence of the buffers on phosphonate adsorption and the K2S2O8 quantity and NaOH dosage required for their digestion in the ISOmini method.
Freundlich model of adsorption 
Adsorption isotherms, i.e., loading q (e.g., in mg P/g adsorbent) applied over the dissolved concentration c (in mg/L P) of adsorptive after a specific contact time, can be modeled using the equation proposed by Freundlich29:
<img alt="Equation 1" src="/files/ftp_upload/57618/57618eq1.jpg" />
If the experimentally obtained values q and c are plotted in the form of a function ln(q) over ln(c), the slope of this function determined by linear regression corresponds to 1/n and the y-axis intercept to the KF value30.
Overview of the procedure 
The entire process for determining the adsorption capacity of granular ferric hydroxide with regard to phosphonates is divided into several steps and is described in the protocol section. For the analysis, it is necessary to prepare a sufficient amount of reagent solutions (Section 1 in the protocol). These are durable for several weeks. The phosphonate-containing solution is then prepared (Section 2), followed by the adsorption test (contact of the phosphonate solution with the granular material) (Section 3) and the analysis of the total P according to the miniaturized ISO method (Section 4).

<table><tbody><tr><td>Sulfuric acid (H&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt;)</td><td>Merck (Darmstadt, Germany)</td><td>1120802510</td><td>98% (p.a.)</td></tr><tr><td>Hydrochloric acid (HCl)</td><td>VWR Chemicals (Fontenay-sous-Bois, France)</td><td>20254.401</td><td>32% (AnalaR NORMAPUR, p.a.)</td></tr><tr><td>Sodium hydroxide (NaOH)</td><td>Merck (Darmstadt, Germany)</td><td>1064981000</td><td>&amp;ge;99% (p.a.)</td></tr><tr><td>Acetic acid (AcOH)</td><td>VWR Chemicals (Fontenay-sous-Bois, France)</td><td>20104.334</td><td>100% (p.a.)</td></tr><tr><td>2-(N-morpholino)ethanesulfonic acid (MES)</td><td>SigmaAldrich (St. Louis, MO, USA)</td><td>M3671-250G</td><td>&amp;ge;99%</td></tr><tr><td>3-(N-morpholino)propanesulfonic acid (MOPS)</td><td>SigmaAldrich (St. Louis, MO, USA)</td><td>M1254-250G</td><td>&amp;ge;99.5%</td></tr><tr><td>4-(2-Hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES)</td><td>SigmaAldrich (St. Louis, MO, USA)</td><td>H3375-250G</td><td>&amp;ge;99.5%</td></tr><tr><td>4-(2-Hydroxyethyl)-1-piperazinepropanesulfonic acid (EPPS)</td><td>SigmaAldrich (St. Louis, MO, USA)</td><td>E9502-250G</td><td>&amp;ge;99.5%</td></tr><tr><td>N-cyclohexyl-2-hydroxyl-3-aminopropanesulfonic acid (CAPSO)</td><td>SigmaAldrich (St. Louis, MO, USA)</td><td>C2278-100G</td><td>&amp;ge;99%</td></tr><tr><td>N-cyclohexyl-3-aminopropanesulfonic acid (CAPS)</td><td>SigmaAldrich (St. Louis, MO, USA)</td><td>C2632-250G</td><td>&amp;ge;98%</td></tr><tr><td>2-Phosphonobutane-1,2,4-tricarboxylic acid (PBTC)</td><td>Zschimmer &amp;amp; Schwarz (Mohsdorf, Germany)</td><td>CUBLEN P 50</td><td>50% technical</td></tr><tr><td>1-Hydroxyethane 1,1-diphosphonic acid monohydrate (HEDP&amp;middot;H&lt;sub&gt;2&lt;/sub&gt;O)</td><td>SigmaAldrich (St. Louis, MO, USA)</td><td>54342-50G</td><td>&amp;ge;95.0%</td></tr><tr><td>Nitrilotris(methylene phosphonic acid) (NTMP)</td><td>SigmaAldrich (St. Louis, MO, USA)</td><td>72568-50G</td><td>&amp;ge;97.0%</td></tr><tr><td>Ethylenediamine tetra(methylene phosphonic acid) (EDTMP&amp;middot;1.4H&lt;sub&gt;2&lt;/sub&gt;O)</td><td>Zschimmer &amp;amp; Schwarz (Mohsdorf, Germany)</td><td>-</td><td></td></tr><tr><td>Diethylenetriamine penta(methylene phosphonic acid) (DTPMP&amp;middot;6H&lt;sub&gt;2&lt;/sub&gt;O)</td><td>Zschimmer &amp;amp; Schwarz (Mohsdorf, Germany)</td><td>-</td><td></td></tr><tr><td>Potassium dihydrogen phosphate (KH&lt;sub&gt;2&lt;/sub&gt;PO&lt;sub&gt;4&lt;/sub&gt;)</td><td>Merck (Darmstadt, Germany)</td><td>1048731000</td><td>&amp;ge;99.5% (p.a.)</td></tr><tr><td>Potassium peroxodisulfate (K&lt;sub&gt;2&lt;/sub&gt;S&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;8&lt;/sub&gt;)</td><td>Merck (Darmstadt, Germany)</td><td>1050920250</td><td>&amp;ge;99.0% (p.a.)</td></tr><tr><td>L(+)-Ascorbic acid (C&lt;sub&gt;6&lt;/sub&gt;H&lt;sub&gt;8&lt;/sub&gt;O&lt;sub&gt;6&lt;/sub&gt;)</td><td>Merck (Darmstadt, Germany)</td><td>1004680500</td><td>&amp;ge;99.7% (p.a.)</td></tr><tr><td>Ammonium heptamolybdate tetrahydrate ((NH&lt;sub&gt;4&lt;/sub&gt;)&lt;sub&gt;6&lt;/sub&gt;Mo&lt;sub&gt;7&lt;/sub&gt;O&lt;sub&gt;24&lt;/sub&gt;&amp;middot;4H&lt;sub&gt;2&lt;/sub&gt;O)</td><td>Merck (Darmstadt, Germany)</td><td>1011800250</td><td>&amp;ge;99.0% (p.a.)</td></tr><tr><td>Granular ferric hydroxide (GFH)</td><td>Hego BioTec (Berlin, Germany)</td><td>-</td><td>FerroSorp RW</td></tr><tr><td>Syringe membrane filters</td><td>Sartorius Stedim Biotech GmbH (G&amp;ouml;ttingen, Germany)</td><td>17765----------Q</td><td>Minisart RC Hydrophilic 25 mm 0.45 &amp;mu;m pore size</td></tr><tr><td>Single-use syringes for membrane filtration</td><td>Henke Sass Wolf (Tuttlingen, Germany)</td><td>5200.X00V0</td><td>3-part Soft-Ject Luer 20 mL</td></tr><tr><td>Rotator</td><td>LLG Labware (Meckenheim, Germany)</td><td>6.263 660</td><td>uniROTATOR2</td></tr><tr><td>Clamp for rotator</td><td>LLG Labware (Meckenheim, Germany)</td><td>6.263 664</td><td>Clamp for uniROTATOR2</td></tr><tr><td>Screw cap vial</td><td>Glasger&amp;auml;tebau Ochs (Bovenden, Germany)</td><td>135215</td><td>Pr&amp;auml;paratenglas Duran, 16x100 mm, thread GL18, cap with PTFE seal</td></tr><tr><td>Micropipette</td><td>Eppendorf (Hamburg, Germany)</td><td>3123000047</td><td>eppendorf Research plus 10&amp;ndash;100 &amp;micro;L</td></tr><tr><td>Micropipette</td><td>Eppendorf (Hamburg, Germany)</td><td>3123000063</td><td>eppendorf Research plus 100&amp;ndash;1000 &amp;micro;L</td></tr><tr><td>Micropipette</td><td>Eppendorf (Hamburg, Germany)</td><td>3123000071</td><td>eppendorf Research plus 0.5&amp;ndash;5 mL</td></tr><tr><td>Precision balance</td><td>Precisa Gravimetrics (Dietikon, Switzerland)</td><td>-</td><td>Precisa LX 220 A SCS</td></tr><tr><td>Thermostat</td><td>Hach (Berlin, Germany)</td><td>LTV077</td><td>HT200S High Temperature Thermostat</td></tr><tr><td>Thermostat</td><td>Merck (Darmstadt, Germany)</td><td>1712000001</td><td>Spectroquant TR 320</td></tr><tr><td>Spectrophotometer</td><td>Jasco Labor- u. Datentechnik (Gro&amp;szlig;-Umstadt, Germany)</td><td>-</td><td>UV/VIS Spectrophotometer Jasco V-550</td></tr><tr><td>Centrifuge tube</td><td>Sarstedt (N&amp;uuml;mbrecht, Germany)</td><td>62.559.001</td><td>Tube 50 mL, 115x28 mm, flat/conical base PP, assembled cap</td></tr><tr><td>pH probe</td><td>WTW (Weilheim, Germany)</td><td>103635</td><td>WTW pH-Electrode SenTix 41</td></tr><tr><td>pH device</td><td>WTW (Weilheim, Germany)</td><td>-</td><td>WTW Multi 350i</td></tr><tr><td>COD determination</td><td>Hach (Berlin, Germany)</td><td>LCK514</td><td>100&amp;ndash;2000 mg/L O&lt;sub&gt;2&lt;/sub&gt;</td></tr><tr><td>Sieve</td><td>Retsch (Haan, Germany)</td><td>60.131.000500</td><td>Test sieve 0.5 mm mesh (ISO 3310/1) stainless steel</td></tr><tr><td>Drying cabinet</td><td>Memmert (Schwabach, Germany)</td><td>-</td><td>Modell 600</td></tr></tbody></table>

optimized procedure for determining the adsorption of phosphonates onto granular ferric hydroxide using a miniaturized phosphorus determination method

This paper introduces a procedure to investigate the adsorption of phosphonates onto iron-containing filter materials, particularly granular ferric hydroxide (GFH), with little effort and high reliability. The phosphonate, e.g., nitrilotrimethylphosphonic acid (NTMP), is brought into contact with the GFH in a rotator in a solution buffered by an organic acid (e.g., acetic acid) or Good buffer (e.g., 2-(N-morpholino)ethanesulfonic acid) [MES] and N-cyclohexyl-2-hydroxyl-3-aminopropanesulfonic acid [CAPSO]) in a concentration of 10 mM for a specific time in 50 mL centrifuge tubes. Subsequently, after membrane filtration (0.45 &#181;m pore size), the total phosphorus (total P) concentration is measured using a specifically developed determination method (ISOmini). This method is a modification and simplification of the ISO 6878 method: a 4 mL sample is mixed with H2SO4 and K2S2O8 in a screw cap vial, heated to 148-150 &#176;C for 1 h and then mixed with NaOH, ascorbic acid and acidified molybdate with antimony(III) (final volume of 10 mL) to produce a blue complex. The color intensity, which is linearly proportional to the phosphorus concentration, is measured spectrophotometrically (880 nm). It is demonstrated that the buffer concentration used has no significant effect on the adsorption of phosphonate between pH 4 and 12. The buffers, therefore, do not compete with the phosphonate for adsorption sites. Furthermore, the relatively high concentration of the buffer requires a higher dosage concentration of oxidizing agent (K2S2O8) for digestion than that specified in ISO 6878, which, together with the NaOH dosage, is matched to each buffer. Despite the simplification, the ISOmini method does not lose any of its accuracy compared to the standardized method.

Watch this Scientific Journal Video about Optimized Procedure for Determining the Adsorption of Phosphonates onto Granular Ferric Hydroxide using a Miniaturized Phosphorus Determination Method at JoVE

Optimized Procedure for Determining the Adsorption of Phosphonates onto Granular Ferric Hydroxide using a Miniaturized Phosphorus Determination Method

This paper introduces a procedure to investigate the adsorption of phosphonates onto iron-containing filter materials, particularly granular ferric hydroxide, with little effort and high reliability. In a buffered solution, the phosphonate is brought into contact with the adsorbent using a rotator and then analyzed via a miniaturized phosphorus determination method.

This paper introduces a procedure to investigate the adsorption of phosphonates onto iron-containing filter materials, particularly granular ferric ...

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Research

JoVE Journal

Environment

14.5K Views.  University of Stuttgart. Deze paper introduceert een procedure voor het onderzoek naar de adsorptie van fosfonaten op ijzer-bevattende filtermaterialen, met name granulaire ijzer(III) hydroxide met weinig inspanning en hoge betrouwbaarheid. In een gebufferde oplossing, is het fosfonaat in aanraking met het absorberend met behulp van een rotator gebracht en vervolgens geanalyseerd via de methode van een verkleinde fosfor sleutelbepaling.

Video: Optimized Procedure for Determining the Adsorption of Phosphonates onto Granular Ferric Hydroxide using a Miniaturized Phosphorus Determination Method

Nucleoside Triphosphates - From Synthesis to Biochemical Characterization

The traditional strategy for the introduction of chemical functionalities is the use of solid-phase synthesis by appending suitably modified phosphoramidite precursors to the nascent chain. However, the conditions used during the synthesis and the restriction to rather short sequences hamper the applicability of this methodology. On the other hand, modified nucleoside triphosphates are activated building blocks that have been employed for the mild introduction of numerous functional groups into nucleic acids, a strategy that paves the way for the use of modified nucleic acids in a wide-ranging palette of practical applications such as functional tagging and generation of ribozymes and DNAzymes. One of the major challenges resides in the intricacy of the methodology leading to the isolation and characterization of these nucleoside analogues.
	
	In this video article, we present a detailed protocol for the synthesis of these modified analogues using phosphorous(III)-based reagents. In addition, the procedure for their biochemical characterization is divulged, with a special emphasis on primer extension reactions and TdT tailing polymerization. This detailed protocol will be of use for the crafting of modified dNTPs and their further use in chemical biology.

The protocol described herein aims to explain and abridge the numerous obstacles in the way of the intricate route leading to modified nucleoside triphosphates. Consequently, this protocol facilitates both the synthesis of these activated building-blocks and their availability for practical applications.

The  traditional strategy for the introduction of chemical functionalities is the  use of solid-phase synthesis by appending suitably modified ...

Chemistry

Preparation of Highly Porous Coordination Polymer Coatings on Macroporous Polymer Monoliths for Enhanced Enrichment of Phosphopeptides

We describe a protocol for the preparation of hybrid materials based on highly porous coordination polymer coatings on the internal surface of macroporous polymer monoliths. The developed approach is based on the preparation of a macroporous polymer containing carboxylic acid functional groups and the subsequent step-by-step solution-based controlled growth of a layer of a porous coordination polymer on the surface of the pores of the polymer monolith. The prepared metal-organic polymer hybrid has a high specific micropore surface area. The amount of iron(III) sites is enhanced through metal-organic coordination on the surface of the pores of the functional polymer support. The increase of metal sites is related to the number of iterations of the coating process.
The developed preparation scheme is easily adapted to a capillary column format. The functional porous polymer is prepared as a self-contained single-block porous monolith within the capillary, yielding a flow-through separation device with excellent flow permeability and modest back-pressure. The metal-organic polymer hybrid column showed excellent performance for the enrichment of phosphopeptides from digested proteins and their subsequent detection using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The presented experimental protocol is highly versatile, and can be easily implemented to different organic polymer supports and coatings with a plethora of porous coordination polymers and metal-organic frameworks for multiple purification and/or separation applications.

A procedure for the preparation of porous hybrid separation media composed of a macroporous polymer monolith internally coated by a high surface area microporous coordination polymer is presented.

We describe a protocol for the preparation of hybrid materials based on highly porous coordination polymer coatings on the internal surface of macroporous ...

Separation of Single-stranded DNA, Double-stranded DNA and RNA from an Environmental Viral Community Using Hydroxyapatite Chromatography

Viruses, particularly bacteriophages (phages), are the most numerous biological entities on Earth1,2. Viruses modulate host cell abundance and diversity, contribute to the cycling of nutrients, alter host cell phenotype, and influence the evolution of both host cell and viral communities through the lateral transfer of genes 3. Numerous studies have highlighted the staggering genetic diversity of viruses and their functional potential in a variety of natural environments. 
Metagenomic techniques have been used to study the taxonomic diversity and functional potential of complex viral assemblages whose members contain single-stranded DNA (ssDNA), double-stranded DNA (dsDNA) and RNA genotypes 4-9. Current library construction protocols used to study environmental DNA-containing or RNA-containing viruses require an initial nuclease treatment in order to remove nontargeted templates 10. However, a comprehensive understanding of the collective gene complement of the virus community and virus diversity requires knowledge of all members regardless of genome composition. Fractionation of purified nucleic acid subtypes provides an effective mechanism by which to study viral assemblages without sacrificing a subset of the community&#x2019;s genetic signature. 
Hydroxyapatite, a crystalline form of calcium phosphate, has been employed in the separation of nucleic acids, as well as proteins and microbes, since the 1960s11. By exploiting the charge interaction between the positively-charged Ca2+ ions of the hydroxyapatite and the negatively charged phosphate backbone of the nucleic acid subtypes, it is possible to preferentially elute each nucleic acid subtype independent of the others. We recently employed this strategy to independently fractionate the genomes of ssDNA, dsDNA and RNA-containing viruses in preparation of DNA sequencing 12. Here, we present a method for the fractionation and recovery of ssDNA, dsDNA and RNA viral nucleic acids from mixed viral assemblages using hydroxyapatite chromotography.

We describe an efficient method to separate single-stranded DNA, double-stranded DNA and RNA molecules from environmental viral communities. Nucleic acids are fractionated using hydroxyapatite chromatography with increasing concentrations of phosphate-containing buffers. This method permits the isolation of all viral nucleic acid types from environmental samples.

Viruses, particularly bacteriophages (phages), are the most numerous biological entities on Earth1,2.  Viruses modulate host cell abundance and diversity, ...

Immunology and Infection

Detection and Recovery of Palladium, Gold and Cobalt Metals from the Urban Mine Using Novel Sensors/Adsorbents Designated with Nanoscale Wagon-wheel-shaped Pores

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in industrialized countries. Here, the development of optical mesosensors/adsorbents (MSAs) for efficient recognition and selective recovery of Pd(II), Au(III), and Co(II) from urban mine was achieved. A simple, general method for preparing MSAs based on using high-order mesoporous monolithic scaffolds was described. Hierarchical cubic Ia3d wagon-wheel-shaped MSAs were fabricated by anchoring chelating agents (colorants) into three-dimensional pores and micrometric particle surfaces of the mesoporous monolithic scaffolds. Findings show, for the first time, evidence of controlled optical recognition of Pd(II), Au(III), and Co(II) ions and a highly selective system for recovery of Pd(II) ions (up to ~95%) in ores and industrial wastes. Furthermore, the controlled assessment processes described herein involve evaluation of intrinsic properties (e.g., visual signal change, long-term stability, adsorption efficiency, extraordinary sensitivity, selectivity, and reusability); thus, expensive, sophisticated instruments are not required. Results show evidence that MSAs will attract worldwide attention as a promising technological means of recovering and recycling palladium, gold and cobalt metals.

Because of the importance and extensive use of palladium, gold and cobalt metals in high-technology equipment, their recovery and recycling constitute an important industrial challenge. The metal recovery system described herein is a simple, low-cost means for the effective detection, removal, and recovery of these metals from the urban mine.

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in ...

Engineering

Two-way Valorization of Blast Furnace Slag: Synthesis of Precipitated Calcium Carbonate and Zeolitic Heavy Metal Adsorbent

The aim of this work is to present a zero-waste process for storing CO2 in a stable and benign mineral form while producing zeolitic minerals with sufficient heavy metal adsorption capacity. To this end, blast furnace slag, a residue from iron-making, is utilized as the starting material. Calcium is selectively extracted from the slag by leaching with acetic acid (2 M CH3COOH) as the extraction agent. The filtered leachate is subsequently physico-chemically purified and then carbonated to form precipitated calcium carbonate (PCC) of high purity (&lt;2 wt% non-calcium impurities, according to ICP-MS analysis). Sodium hydroxide is added to neutralize the regenerated acetate. The morphological properties of the resulting calcitic PCC are tuned for its potential application as a filler in papermaking. In parallel, the residual solids from the extraction stage are subjected to hydrothermal conversion in a caustic solution (2 M NaOH) that leads to the predominant formation of a particular zeolitic mineral phase (detected by XRD), namely analcime (NaAlSi2O6&#8729;H2O). Based on its ability to adsorb Ni2+, as reported from batch adsorption experiments and ICP-OES analysis, this product can potentially be used in wastewater treatment or for environmental remediation applications.

A protocol for the parallel production of precipitated calcium carbonate and zeolitic material from blast furnace slag via mineral carbonation and alkaline hydrothermal conversion, respectively, is presented. The performance of the zeolitic material towards nickel adsorption is tested.

The aim of this work is to present a zero-waste process for storing CO2 in a stable and benign mineral form while producing zeolitic minerals with ...

Screening for Thermotoga maritima Membrane-Bound Pyrophosphatase Inhibitors

Membrane-bound pyrophosphatases (mPPases) are dimeric enzymes that occur in bacteria, archaea, plants, and protist parasites. These proteins cleave pyrophosphate into two orthophosphate molecules, which is coupled with proton and/or sodium ion pumping across the membrane. Since no homologous proteins occur in animals and humans, mPPases are good candidates in the design of potential drug targets. Here we present a detailed protocol to screen for mPPase inhibitors utilizing the molybdenum blue reaction in a 96 well plate system. We use mPPase from the thermophilic bacterium Thermotoga maritima (TmPPase) as a model enzyme. This protocol is simple and inexpensive, producing a consistent and robust result. It takes only about one hour to complete the activity assay protocol from the start of the assay until the absorbance measurement. Since the blue color produced in this assay is stable for a long period of time, subsequent assay(s) can be performed immediately after the previous batch, and the absorbance can be measured later for all batches at once. The drawback of this protocol is that it is done manually and thus can be exhausting as well as require good skills of pipetting and time keeping. Furthermore, the arsenite-citrate solution used in this assay contains sodium arsenite, which is toxic and should be handled with necessary precautions.

Screening for Thermotoga maritima Membrane-Bound Pyrophosphatase Inhibitors

Here we present a screening method for membrane-bound pyrophosphatase (from Thermotoga maritima) inhibitors based on the molybdenum blue reaction in a 96 well plate format.

Membrane-bound pyrophosphatases (mPPases) are dimeric enzymes that occur in bacteria, archaea, plants, and protist parasites. These proteins cleave ...

Biochemistry

Study of Short Peptide Adsorption on Solution Dispersed Inorganic Nanoparticles Using Depletion Method

Fundamentals of inorganic-organic interactions are critically important in the discovery and development of novel biointerfaces amenable for utilization in biotechnology and medicine. Recent studies indicate that proteins interact with surfaces through limited adsorption sites. Protein fragments such as amino acids and peptides can be used for interaction modeling between complex biological macromolecules and inorganic surfaces. During the last three decades, many valid and sensitive methods have been developed to measure the physical chemistry fundamentals of those interactions: isothermal titration calorimetry (ITC), surface plasmon resonance (SPR), quartz crystal microbalance (QCM), total internal reflection fluorescence (TIRF), and attenuated total reflectance spectroscopy (ATR).
The simplest and most affordable technique for the measurement of adsorption is the depletion method, where the change in sorbate concentration (depletion) after contact with solution-dispersed sorbent is calculated and assumed to be adsorbed. Adsorption isotherms based on depletion data provide all basic physicochemical data. However, adsorption from solutions requires longer equilibration times due to kinetic restrictions and sorbents with a high specific surface area, making it almost inapplicable to macroscopic fixed plane surfaces. Moreover, factors such as the instability of sols, nanoparticle aggregates, sorbent crystallinity, nanoparticle size distribution, pH of the solution, and competition for adsorption, should be considered while studying adsorbing peptides. Depletion data isotherm construction provides comprehensive physical chemistry data for literally every soluble sorbate yet remains the most accessible methodology, as it does not require expensive setups. This article describes a basic protocol for the experimental study of peptide adsorption on inorganic oxide and covers all critical points that affect the process.

The first step in comprehending biomolecule-inorganic solid phase interaction is revealing fundamental physicochemical constants that may be evaluated by establishing adsorption isotherms. Adsorption from the liquid phase is restricted by kinetics, surface capacity, pH, and competitive adsorption, which all should be cautiously considered before setting an adsorption experiment.

Fundamentals of inorganic-organic interactions are critically important in the discovery and development of novel biointerfaces amenable for utilization ...

Absolute Quantitation of Inositol Pyrophosphates by Capillary Electrophoresis Electrospray Ionization Mass Spectrometry

Inositol pyrophosphates (PP-InsPs) are an important group of intracellular signaling molecules. Derived from inositol phosphates (InsPs), these molecules feature the presence of at least one energetic pyrophosphate moiety on the myo-inositol ring. They exist ubiquitously in eukaryotes and operate as metabolic messengers surveying phosphate homeostasis, insulin sensitivity, and cellular energy charge. Owing to the absence of a chromophore in these metabolites, a very high charge density, and low abundance, their analysis requires radioactive tracer, and thus it is convoluted and expensive. Here, the study presents a detailed protocol to perform absolute and high throughput quantitation of inositol pyrophosphates from mammalian cells by capillary electrophoresis electrospray ionization mass spectrometry (CE-ESI-MS). This method enables the sensitive profiling of all biologically relevant PP-InsPs species in mammalian cells, enabling baseline separation of regioisomers. Absolute cellular concentrations of PP-InsPs, including minor isomers, and monitoring of their temporal changes in HCT116 cells under several experimental conditions are presented.

A procedure for capillary electrophoresis electrospray ionization mass spectrometry for the absolute quantitation of inositol pyrophosphates from mammalian cell extracts is described.

Inositol pyrophosphates (PP-InsPs) are an important group of intracellular signaling molecules. Derived from inositol phosphates (InsPs), these molecules ...

Synthesis and Discovery of Phosphonate-Based MOFs: A Solvothermal Approach

Discovery and Synthesis Optimization of Isoreticular Al(III) Phosphonate-Based Metal-Organic Framework Compounds Using High-Throughput Methods

High-throughput (HT) methods are an important tool for the fast and efficient screening of synthesis parameters and the discovery of new materials. This manuscript describes the synthesis of metal-organic frameworks (MOFs) from solution using an HT reactor system, resulting in the discovery of various phosphonate-based MOFs of the composition [Al2H12-x(PMP)3]Clx&#8729;6H2O (H4PMP = N,N &#39;-piperazine bis(methylenephosphonic acid)) for x = 4, 6, denoted as Al-CAU-60-xHCl, containing trivalent aluminum ions. This was accomplished under solvothermal reaction conditions by systematically screening the impact of the molar ratio of the linker to the metal and the pH of the reaction mixture on the product formation. The protocol for the HT investigation includes six steps: a) synthesis planning (DOE = design of&#160;experiment) within the HT methodology, b) dosing and working with in-house developed HT reactors, c) solvothermal synthesis, d) synthesis workup using in-house developed filtration blocks, e) characterization by HT powder X-ray diffraction, and f) evaluation of the data. The HT methodology was first used to study the influence of acidity on the product formation, leading to the discovery of Al-CAU-60&#8729;xHCl (x = 4 or 6).

Author Spotlight: Accelerating Discovery in Microporous Material Chemistry 

The targeted synthesis of new metal-organic frameworks (MOFs) is difficult, and their discovery depends on the knowledge and creativity of the chemist. High-throughput methods allow complex synthetic parameter fields to be explored quickly and efficiently, accelerating the process of finding crystalline compounds and identifying synthetic and structural trends.

High-throughput (HT) methods are an important tool for the fast and efficient screening of synthesis parameters and the discovery of new materials. This ...

High-Throughput Measurement and Classification of Organic P in Environmental Samples

Many types of organic phosphorus (P) molecules exist in environmental samples1. Traditional P measurements do not detect these organic P compounds since they do not react with colorimetric reagents2,3. Enzymatic hydrolysis (EH) is an emerging method for accurately characterizing organic P forms in environmental samples4,5. This method is only trumped in accuracy by Phosphorus-31 Nuclear Magnetic Resonance Spectroscopy (31P-NMR) -a method that is expensive and requires specialized technical training6. We have adapted an enzymatic hydrolysis method capable of measuring three classes of phosphorus (monoester P, diester P and inorganic P) to a microplate reader system7. This method provides researchers with a fast, accurate, affordable and user-friendly means to measure P species in soils, sediments, manures and, if concentrated, aquatic samples. This is the only high-throughput method for measuring the forms and enzyme-lability of organic P that can be performed in a standard laboratory. The resulting data provides insight to scientists studying system nutrient content and eutrophication potential.

This protocol describes a high-throughput method of enzymatic hydrolysis that utilizes a microplate reader to measure and classify soil phosphorus as P monoesters, P diesters and inorganic P. Up to 96 samples can be measured at one time in a standard laboratory.

Many types of organic phosphorus (P) molecules exist in environmental samples1.  Traditional P measurements do not detect these organic P compounds since ...

Optimized Procedure for Determining the Adsorption of Phosphonates onto Granular Ferric Hydroxide using a Miniaturized Phosphorus Determination Method

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